This invention relates to a new catalyst system containing bisiminopyridyl complexes of cobalt and/or iron with bulky substituents on the bisiminopyridyl ligand, to a method for the production thereof, to a method for the polymerization of xcex1-olefins, particularly ethylene, and to the use of the polyolefins which can be produced by such method for the production of moldings of all types.
WO-A-98/27124 describes a method for the polymerization of ethylene by means of bisiminopyridylcobalt or -iron complexes of general formula (I) and co-catalysts, and describes the support of catalyst systems of this type in a liquid phase or in a fluidized bed process. WO-A-98/30612 describes a method for the polymerization of propylene by means of the catalysts disclosed in WO-A-98/27124.
WO-A-99/02472 describes bisiminopyridyl complexes of iron and the use thereof for the oligomerization and polymerization of ethylene. WO-A-99/12981 describes a catalyst system comprising bisiminopyridyl complexes of iron, cobalt, ruthenium or manganese for the homo- and copolymerization of ethylene and xcex1-olefins. 
G. J. P. Pritovsek et al., Chem. Commun. 1998, pages 849-50 (1998) describe bisiminopyridyl complexes of iron and cobalt of general formula (I), and describe the synthesis and use thereof as polymerization catalysts.
B. L. Small, M. Brookhart, A. M. A. Bennett, J. Am. Chem. Soc. 120, pages 4049-50 (1998), and B. L. Small, M. Brookhart, J. Am. Chem. Soc. 120, pages 7143-4 (1998) also describe bisiminopyridyl complexes of iron and cobalt of general formula (I), as well as the synthesis and use thereof as polymerization catalysts.
C. Pellecchia, M. Mazzeo, D. Pappalardo, Macromol. Rapid. Commun. 19, 651-55 (1998), and B. L. Small, M. Brookhart, Macromolecules 1999, 32, 2120-30 (1999) also describe bisiminopyridyl complexes of iron and cobalt of general formula (I) and the use thereof as polymerization catalysts for propylene.
A common feature of all these documents is that in the bisiminopyridyl complexes which are disclosed, the R3 and R4 radicals, independently of each other, represent hydrogen or hydrocarbon radicals which are optionally substituted, or represent functional groups. R3 and R4 are most preferably, hydrogen and/or methyl radicals. One significant disadvantage of the synthesis which is described according to the prior art is that it is not possible to produce bisiminopyridyl ligands and complexes which comprise bulky R3 and R4 radicals. Reaction times, which are unsatisfactorily long, as well as low overall yields, are described for these complexes which can be obtained according to the prior art.
Consequently, one object of the present invention is to provide bisiminopyridyl complexes of iron and cobalt which exhibit improved catalytic properties. A further object of the invention is to provide an improved method of producing said bisiminopyridyl complexes of iron and cobalt. A further object of the present invention is to provide an alternative method for the production of the bisiminopyridyl complexes of iron and cobalt. A further object of the present invention is to provide a method for the production of polyolefins with the aid of the bisiminopyridyl complexes of iron and cobalt. A further object of the present invention is to provide high molecular weight polyolefins using the bisiminopyridyl complexes of iron and cobalt.
Surprisingly, it has now been found that catalyst systems which exhibit higher activity, and polyolefins which have a significantly narrower molecular weight distribution, can be obtained if R3 and R4 constitute bulky substituents. Moreover, a method has been provided which enables bisiminopyridyl complexes of iron, cobalt, nickel or palladium, which correspond to general formula (I) and which comprise bulky R3 and R4 radicals, to be produced in high yield.
The present invention therefore relates to a catalyst system containing a compound of general formula (I) 
wherein
M is selected from iron, cobalt, nickel or palladium,
Q is a mono-anionic or non-anionic ligand,
R1 and R2, independently of each other, represent an aryl radical which is optionally substituted,
R3 and R4, independently of each other, represent a bulky substituent,
R5, R6 and R7, independently of each other, are selected from hydrogen, a C1-C10 alkyl group which is optionally substituted, or a C6-C14 aryl radical which is optionally substituted, or are parts of a ring system, and
n represents an integer within the range from 1 to 3,
and containing one or more compounds which form a transition metal complex cation.